The right side of Parker Walsh’s body and brain are bigger than the left. Doctors at Seattle Children’s Research Institute are studying a genetic mutation that could point to a cause for his condition.

When Parker Walsh flashes his toothy smile, he can get everyone around him grinning as well. That smile has pulled Parker, 21, and his family through a lot of tough times.

Parker was born with a host of medical issues that have impacted his development—a craniofacial abnormality, gastrointestinal issues, neurological delays and speech difficulty. Doctors could not pinpoint a specific cause for his conditions, and offered the best treatments available based on their diagnoses.

Now, doctors at Seattle Children’s Research Institute studying a gene that controls cellular growth have provided clues for what might have contributed to some of Parker’s medical issues, and the information could lead to improved diagnosis and therapies for babies and kids that share Parker’s experience.

An unclear medical picture

Parker spent much of his childhood in and out of Seattle Children’s Hospital because of his medical issues.

“He was a rascal at the hospital,” said his mom, Cindy Walsh, who is also a nurse in the Seattle Children’s post-anesthesia care unit. “He hid snakes in his bed for the nurses to find, the little trickster.”

The constant medical care was taxing with doctor’s appointments, exams and hospitalizations. But through it all, Parker stayed upbeat, even when doctors couldn’t give the family a specific diagnosis.

Parker was also developmentally delayed. He couldn’t speak, but could mimic those around him. When he turned 12, he made a big leap forward.

“All of a sudden, he just turned on,” Walsh said. “He became an animated jokester, and he’s a sharp guy. He can beat you at Jeopardy and retains a lot of knowledge on music, sports and cars.”

Clues from a genetic test

Parker tested positive for a genetic mutation that can cause overgrowth in the body, which could explain why one side of his body is bigger than the other.

The right side of Parker’s body, face and brain are bigger than the left. He was recently tested for a genetic mutation that doctors at Seattle Children’s Research Institute are studying, and the test revealed a possible cause for some of his conditions.

Dr. Ghayda Mirzaa is a geneticist who studies the PIK3CA gene. This gene is important for growth, cell division, and development of the blood vessels and brain in the human body. But if this gene is mutated, it can cause problems. Mirzaa recently defined some disorders associated with this gene mutation in the Journal of Clinical Investigation.

“There’s a particular mutation we’ve identified in Parker that can make the PIK3CA gene overwork,” Mirzaa said. “The gene mutation doesn’t have an ‘off’ switch, so it causes increased cell growth and malformations in the blood vessels.”

The mutated gene can cause overgrowth in any part of the body—brain, face, arm, leg, blood vessels, or other tissue. It has been linked to focal cortical dysplasia, a brain malformation that can cause epilepsy. It’s also been linked to adult cancers including breast and colon cancer.

A positive test for PIK3CA

Parker was tested for the genetic mutation when he was 18 during one of the most harrowing medical experiences he has endured: A diagnosis of lymphoma, a type of blood cancer that causes tumors.

“One night we were watching TV and something told me he wasn’t right,” Walsh said. “He had night sweats and lack of appetite. I took him to the local hospital and he began having major trouble breathing. We were airlifted to Seattle Children’s in a helicopter, and when we landed, doctors and nurses rushed out to get Parker.”

Parker began chemotherapy. During Parker’s hospitalization, Dr. Jonathan Perkins was one of the doctors who cared for him. Perkins, who specializes in blood vessel anomalies and had treated Parker in the past for facial asymmetry and lymphedema in his legs, took a sample of Parker’s skin to test it because he had developed chronic blisters. The test showed that Parker’s skin had the PIK3CA mutation.

“We already know a lot more about this gene than we did just a few years ago,” Perkins said. “We discovered that this gene mutation may predispose patients to cancer, among other problems like tissue overgrowth. This research is changing how we treat some patients who have overgrowth issues.”

Mirzaa and Perkins say this research improves our understanding of how this gene mutation can manifest in the body and that knowledge has resulted in fine-tuned care for patients. Certain drugs that weren’t considered before can now be included in a patient’s treatment, and patients who are tested for mutations, like Parker, can propel research and improved therapies.

With knowledge that there are drugs in development that target this gene, Parker’s doctors hope that improved therapies will soon be available for Parker and other patients like him.

Parker back on his feet

Parker got to spend a day at Safeco Field visiting with the Mariners. He’s pictured here with second baseman Robinson Cano.

After beating cancer and gaining his strength, Parker is back to his old self, ever the comic to family and friends with his sense of humor. He fulfilled a dream by meeting Russell Wilson, who Parker likes to point out plays both football and baseball (his favorite sport).

“The work the researchers are doing with this genetic pathway is a puzzle, and Parker is another piece of it,” Walsh said. “Doctors working on his case are learning a lot from him, and that’s exciting. I hope they find more effective therapies in his lifetime. He’s a trooper, and he’ll keep running.”

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